Use python-magic API when available

The usage of the python-magic -> libmagic API comatibility [1] raises a
deprecation warning. This patch uses the python-magic default API when
it's available and in other case it uses the libmagic default API.

Fix #1083

[1] https://github.com/ahupp/python-magic/blob/master/COMPAT.md

rpmlint/pkg.py

@@ -355,9 +355,19 @@ def parse_deps(line):
 
 
 def get_magic(path):
+    # python-magic & libmagic compatibility code
+    # https://github.com/ahupp/python-magic/blob/master/COMPAT.md
+    detect_magic = None
+    if hasattr(magic, 'from_file'):
+        # python-magic module
+        detect_magic = magic.from_file
+    else:
+        # libmagic python bindings
+        detect_magic = lambda x: magic.detect_from_filename(x).name
+
     try:
-        return magic.detect_from_filename(path).name
-    except ValueError:
+        return detect_magic(path)
+    except (ValueError, FileNotFoundError):
         return ''